1. Technical Field
The present invention relates to a workpiece conveyor which conveys a workpiece by a belt conveyor, air, or the like and a method of conveying a workpiece.
2. Related Art
A known workpiece conveyor is of a type which blows out air upwardly from a workpiece conveying path, on which a workpiece is conveyed, to float the workpiece while blowing out air from both sides of the workpiece conveying path more powerfully than from the central area thereof to guide the workpiece to the central area. In this state, the workpiece conveyor blows out air from spouts provided in the workpiece conveying path in the conveying direction to give propulsion to the workpiece for conveyance. Reference is made to JP-A-10-157851 as an example of related art. According to this workpiece conveyor, a workpiece can be conveyed without deviating from the workpiece conveying path.
There is another known type of workpiece conveyor in which a plurality of groups of poles provided on both sides of a roller conveyor to make a pair are moved to the central area from both sides of a workpiece conveyed by the roller conveyor, thereby positioning the workpiece at the central area of the roller conveyor. Reference is made to JP-A-2003-063636 as an example of related art. Accordingly, even if a workpiece is mounted on the roller conveyor while deviating from the workpiece conveying path, it can be positioned at the central area by the poles. As a result, the workpiece can be prealigned while being conveyed.
There is still another known type of workpiece conveyor which conveys a workpiece mounted on a pair of belt conveyors while making the workpiece applied with auxiliary guides provided along the outsides of the pair of belt conveyors. Reference is made to JP-A-10-087042 as an example of related art. Accordingly, it is possible to properly convey various workpieces approximately identical in size.
With the configuration of JP-A-10-157851, however, there arises a first problem that it is necessary to blow out air from both sides of the workpiece conveying path more powerfully than from the central area thereof to convey a workpiece without deviating from the workpiece conveying path. It is also necessary to consider air turbulence resulting from a possible air collision. Unfortunately, it is complicated to control air due to matters involving the blowing amount of air, the blowing direction thereof, the number and the arrangement of spouts, which cause an increased air consumption.
Meanwhile, when a plurality of workpieces are conveyed by the workpiece conveyor, they are conveyed on the workpiece conveying path with a gap provided therebetween. If a preceding workpiece is caused to be in a standby state on the workpiece conveying path in this case, it is necessary for the following workpiece to maintain a safe distance from the preceding one and avoid getting contact with it. Incidentally, as a second problem, if the gap between the plurality of workpieces is to be maintained by physical contact, the workpieces could be damaged. For example, when a glass substrate, etc. is used as a workpiece, there is a possibility of causing chipping or invisible cracking at contact points. It is of particular note that, this kind of cracks tend to be overlooked at the inspection stage, and the trouble is that cracks are liable to be found after workpieces have been manufactured.
With the configuration of JP-A-2003-063636, furthermore, there arises a third problem that a workpiece is damaged due to physical contact because the plurality of groups of poles are made contact with the conveyed workpiece to make the same positioned at the central area of the roller conveyor. For example, when a glass substrate, etc. is used as a workpiece, there is a possibility of causing chipping or invisible cracking at contact points. It is of particular note that, this kind of cracks tend to be overlooked at the inspection stage, and the trouble is that cracks are liable to be found after workpieces have been manufactured.
With the configuration of JP-A-10-087042, furthermore, there arises a fourth problem, in addition to those described above, that a workpiece smaller in size than that mountable on the pair of belt conveyors cannot be conveyed because the pair of belt conveyors are fixedly provided. It is not possible, therefore, to perform conveyance according the size of a workpiece.